Separation of phenols from their mixtures with neutral oils



May 26,1959 w. HERBET TAL 2,888,491

SEPARATION OF PHENOLS FROM THEIR MXTURES WITH NUTRAL OILS dilution woer May 26, 1959 SEPARATION 0E PHENoLs FROM IH Filed oct. 5, 1956 W. HERBERT ETAL EIR MIXTURES WITH NEUTRAL OILS 2 Sheets-Sheet 2 ffy.

lf 25I phenol containing oil u 2,6 s

` I l l l l A Y I r I 1 l 3 I f 5 l ,HMH/Veys United States Patent O SEPARATION OF PHENOLS FROM THEIR lVIlXTURES WITH NEUTRAL OILS Wilhelm Herbert, Karl Grob, and Karl Heinz Eisenlohr,

Frankfurt am Main, Germany, assignors to Metallgesellschaft Aktiengesellschaft, Frankfurt am Main, Germany Application October 3, 1956, Serial No. 613,704

16 Claims. (Cl. 260-627) This invention relates to new and useful improvements in the separation of phenols from their mixtures with neutral oil and is a continuation-in-part of our copending application Serial No. 260,056, tiled December 5, 1951, and now abandoned.

As is known acid oils as, for example, phenols, cresols, xylenols, pyrocatechols and oxygen-containing organic compounds of the sarne or similar character, having higher boiling points, must often be separated from their mixture with neutral oils. These neutral oils consist predominantly of saturated or unsaturated aliphatic, aromatic, naphthenic and/ or other hydrocarbons and possibly organic bases such as pyridine bases and/ or oxygen-- containing or sulphur-containing neutral or basic organic compounds. The acid oils are often referred toas phenols or phenol oils and will be referred to herein as phenols.

The products obtained from the distillation, gasification or hydrogenation of solid fuels such as lignite, brown coal, anthracite, oil shale or from liquid fuels such as petroleums containing acid constituents or the like often contain mixtures of phenols and neutral oils.

In order to recover the neutral oils from these mixtures, it is known to subject the mixture or fraction thereof to an extraction with hot water at a temperature of 100 C., preferably between about l50-250 C. under a pressure exceeding the vapor pressure of the material treated. The extraction is preferably elected as a counter-current operation. Under these conditions, the absorption power of the water for the phenols is particularly good and an extensive extraction of the phenols is obtained. In this extraction, however, the Water not only dissolves the phenols but also dissolves a certain quantity of the neutral oil. As a result of the extraction, therefore, an aqueous yextract is obtained which -contains a large amount of phenols and a smaller quantity of the neutral oils which may amount to -20% or more based on the phenols. This results in a loss of the neutral oils and a contamination of the phenols when the `same are subsequently separated from the aqueous extract as, for example, with a further extraction with esters, ketones, alcohols or other extraction liquids which dissolve the phenols but are immiscible, or substantially immiscible with water. This process is, therefore, not suitable for the recovery of phenols in an uncontaminated form suitable for further use or processing. In this connection, the phenols and particularly the phenols in the phenol-containing oil fractions boiling between about l30230 C. have achieved importance in industry.

One object of this invention is an eiective and economical separation of the neutral oils from the aqueous extract obtained in the extraction of phenols from pheno1-containing neutral oil mixtures using hot water at a temperature of at least 100 C. and preferably 150- 250 C. under pressure in excess of the vapor pressure of the extraction mixture.

A further object of this invention is' the recovery of phenols from the aqueous extract obtained in the hot water extraction otf phenols from phenol-neutral oil mixtures in a form substantially uncontaminated by neutral oil and thus suitable for further use and/ or treatment as, for example, the transformation and pursuit for purer phenols.

These and still further objects will become apparent from the following description read in conjunction with the drawings in which:

Fig. l diagrammatically shows an embodiment of plant set-up for eiiecting the process in accordance with the invention.

Fig. 2 diagrammatically shows a further embodiment of a plant set-up for eiecting the process in accordance with the invention, which includes a further extraction .operation utilizing organic solvents.

In accordance with the invention, it has surprisingly been discovered that the dissolved neutral oils may be very effectively and economically removed from the aqueous extract containing phenols and dissolved neutral oils obtained by the extraction of phenols from their mixtures with neutral oils using water at a temperature above C. and preferably from 150 200 C. under a pressure in excess of the vapor pressure of the extraction mixture, by distilling oi the neutral oils with water vapor ,from the hot water extract if, prior to the distillation, the extract is diluted with an additional amount of water suilicient to maintain the phenols dissolved during the subsequent distillation treatment.

Very surprisingly, the dilution of the hot water extract causes the phenols to lose their ability to serve as solubilizers for the neutral oils, so that the distillation removes the neutral oils to a very far-reaching extent and only small quantities, generally much less than 1% of the neutral oils, remain in the solution of phenols. After the distillation of the neutral oils, the phenols may be recovered from the extract in a particularly pure form in the conventional manner as, for example, in a subsequent extraction using organick solvents, such as butylacetate as the extraction medium.

The neutral oils and the water vapor distill over as an azeotropic mixture containing, for example, about 5- 15% of the nonaqueous components. Only a relatively small quantity amounting to a few percent as, for example, from 2-3% of water contained in the aqueous extract need be distilled in order to remove a major quantity of the neutral oil from the aqueous extract.

Very surprisingly and unexpectedly only an extremely small quantity of the phenols are entrained and carried over with the distilling mixture.

The distillation may be effected at normal, reduced or increased pressure. Itis generally preferable to operate at normal or reduced pressure. When operating, for example, at normal pressure, the azeotropic mixture passes over at a temperature ranging between 93 98 C. When operating the distillation at normal or reduced pressure, it is necessary to relieve the aqueous extract from the pressure under which the extraction was eiected and to adapt it to the pressure of the distillation, and to decrease the temperature from the extraction temperature to the distillation temperature. In order that this pressure release and temperature lowering do not cause a separation of the phenols, which are much less soluble ata lower temperature and pressure, it is generally desirable to effect the dilution of the aqueous extract with about 2-6 volumes of water per volume of extract. -A greater quantity of water within this range is preferably used when the extraction of the phenols from their mixtures lwith the neutral oils is effected at higher temperatures as, for example, 200-250 C. with a lower dilution sufcing when the extraction is effected in the lower temperature range as, for example, at 150 C.

The aqueous extract from the hot water extraction is preferably cooled prior to the distillation. This cooling, which is advantageously ettected by the dilution, is preferably to a temperature between about 60-90 C. This cooling, in many cases, results in a separation of small quantities of the neutral oil from the aqueous extract as an upper layer which may be removed, and particularly if the cooling has been effected prior to the dilution. This increases the economy of the distillation operation as this quantity of neutral oil need not be separated in the subsequent distillation. A cooling to temperatures below about 60 C. does not result in any particular advantage since the solubility in the neutral oil in the phenol-con taining aqueous solution does not considerably decrease upon further cooling below 60 C. It is, of course, not necessary to remove the neutral oil which separates upon the cooling but the aqueous extract containing the suspended neutral oil may be directly passed to the distillation.

The distillation is preferably effected by the direct introduction of steam, although the same may be effected in any other known or conventional manner as, for example, by indirect heating.

The dilution is preferably effected with a phenol-containing water as, for example, from the process itself.

Any carbon dioxide and hydrogen sulfide which are distilled over with the azeotropic mixture are preferably separately recovered and passed in contact with the cooled phenol-containing aqueous extract from which they were distilled.

Referring to the embodiment shown in Fig. 1, the hot water extraction is effected in a manner known per se in two extraction columns l and 3. The number of extraction columns used depends solely upon the structural features, since it is not advisable to use columns of undue height. Thus, for example, instead of two columns, one, or three, or more may be used. The phenol-containing oil extractant as, for example, the extractant of boiling between l20-200 C. obtained from lignite oil is preheated in the heat exchanger 3 to, for example, l60 C. and introduced into the bottom of the column 2. The same passes upward through the column 2 and is pumped by means of pump 4 upward through the column l. The extraction water as, for example, dephenolized water, obtained from low temperature carbonization water dephenolization, i.e. the so-called thin water is passed through the heat exchanger 6 into the upper portion of the column l, passes downward through the column 1 up to the upper portion of the column 2, down through the column 2, and thus in counter-current contact with the fraction being dephenolized. The temperature in the column is maintained at about 160 C. at a pressure of about 20 atmospheres. The contacting of the extraction water with the fraction extensively dephenolizes the oil and the dephenolized oil is removed from the top of the column 1 through the heat exchanger S. After passage through the columns the oil is, for example, free from 95% of its content of phenol. The heat exchanger cools the dephenolized oil and the heat removed may be passed to the heat exchanger 3 for heating the incoming oil feed. Alternately the heat exchangers 3 and 5 may be substituted by a single heat exchanger, which heats the incoming oil by means of the outgoing dephenolized oil. The columns 1 and 2 may contain suitable iilling bodies or packing, in order to assure intermittent contacting between the aqueous extracting agent and the oil.

The hot aqueous extract which has extracted the phenols from the oil in the columns so that, for example, it has a phenol content of about 3.5%, is conducted through the heat exchanger 7 to the expansion and mixing vessel 8. The heat exchanger 7 removes heat from the aqueous extract, preferably supplying the same to the incoming extracting medium as, for example, by means of the heat exchanger 6 or by being combined with the heat exchanger 6. An additional heating medium may be passed through the heat exchangers 6 or 3 to maintain the extraction temperature or the columns may be heated to make up the heat loss. The dilution water is also passed into the vessel 9, passing through the heat exchanger 17 by means of which the temperature is adjusted so that the temperature of the mixture after the dilution is between about 60-90 C. and preferably about C. Preferably the dilution water is in the form of a phenol-containing waste water as, for example, from low temperature carbonization having a phenol content of between about l-l.2%. An amount of dilution Water is added so that phenol separation will not occur at the temperatures and pressures encountered in the steps up to and through the distillation.

Thus, for example, an amount of water may be added so that the phenol content of the resulting mixture is about 1.8% extractable phenol. In addition, a portion of the neutral oils are taken up in the course of the hot water extraction which amount to, for example, more than 10% based on the phenols present in the mixture. Upon the cooling of the aqueous extract as the same occurs in the heat exchanger '7 and/ or upon dilution in the vessel 8, a small portion of the neutral oil may separate from the solution due to the reduced solubility caused by the lowering of temperature. The mixture of the hot aqueous extract and the phenol-containing diluting water, which may additionally contain the suspended separated oil, is passed from the vessel 8 into the separator 9. In the separator 9 the small quantities of suspended oil separate from the remaining portion of the aqueous extract as an upper layer and may be intermittently removed through the overflow conduit l0 as the same accumulates. The bulk of the mixture consisting of the lower aqueous phase is pumped by means of the pump l1 through the heat exchanger l2 into the distillation column 13. The neutral oil is extensively distilled oftE from the phenol in the column 13 by means of steam passed into the line 14 which carries the neutral oil as an azeotropic mixture, together with about 2-3% of the water present in the mixture. Only a small insignificant amount of the phenol is carried over with the oil-water azeotrope and only an extremely low content of oil is retained in the aqueous phenol extract, which generally amounts to much less than 1% based on the phenol. The distillate is precipitated in the dephlegmator 15 and separated in the known manner. The distilled neutral oils are preferably added to the phenol-containing light oil fraction being fed to the hot water extraction and the condensed water is preferably admixed with the low temperature phenol-containing carbonization off water. The aqueous phenol solution in the sump of the column 14 will pass through the heat exchanger 16 to, for example, a phenol extraction using butylacetate from which extremely pure phenols may be obtained.

Referring to the embodiment as shown in Fig. 2, the mixture containing phenols and neutral oils as, for example, a phenol-containing hydrocarbon fraction boiling between 150-210 C. is passed from the container 22 through the heat exchanger 24, where the same is heated, through the conduit 25 into the left hand side of the extraction apparatus 26 which may, for example, consist of a multiple number of series-connected pumps and separators. The water for the extraction is passed by means of the line 30 through the heat exchanger 32 into the right hand side of the apparatus. The extraction water consists of thin phenol-containing water from the process itself. Additional water or fresh water for starting up the operation may be passed in through the line 29. The extraction water and the hydrocarbon fraction are heated up in the heat exchangers 32 and 24 respectively, so that the temperature of the extraction is maintained above C. and preferably between about l50250 Vdiluting the hot aqueous extract. preferably consists of a phenol-containing water as, for

- C. In the apparatus 26 the extraction water and the hydrocarbon pass in'counter-current contact with each other, being passed n series through each of the pumps and separators which act as the individual extraction stages. As the hydrocarbon fraction passes through the apparatus from the left to the right, in counter-current contact with the extraction water the same becomes continuously poorer in phenols while the water, as the same passes from the right to the left, becomes continuously richer in phenols. The hot water extract obtained in this manner leaves the extraction apparatus through line 27 and passes through the heat exchanger 28, which cools the same, and preferably supplies the heat to the heat exchanger 32 as, for example, by being combined with the same. The hot water extract thus may, for example, be passed through tubes into the mixing" and pressure release vessel 20, while the extraction water is fed to the extraction apparatus by means of the conduit 30 passed round these tubes in heat exchange contact therewith. At the same time, the dilution water is passed into the pressure release and mixing vessel by means of the line 33, pump 34 and line 35, mixing with and The diluting water example, waste water from a low temperature carbonization, or phenol-containing water from the process itself. The temperature of diluted mixture is reduced by the cooling in the heat exchanger 28 and by th'e'dilution itself. In the pressure reducing mixing vessel 20, the pressure underwhich the extraction was effected is also relieved. The diluted mixture is passed from the vessel 20 through the line 36, pump 37 and `line 38, finto the ture, form an upper layer 'and may be'removed by means of the overilow line 4'0, and by meansofthe pump 41 and line 42 to an intermediate stage ofthe extraction and apparatus. From the separator 39 thephenol-containing phenols.

"fed vthrough the line '49 for use or for further processing as, for example, rening and fractionation. The dephenolized so-called thin water is recycled through the line to the hot water extraction apparatus and the major portion is discharged through the conduit 46.

The following example is given by way of illustration and not limitation:

Example 1 160"` C. These 7 m.3/hr. of thin water absorb in this connection 95% of the phenols contained in the fraction. The extract is accordingly a 3.3% extract. It is cooled by heat exchange to 80 C. and flash evaporated into the stream of 22 111.3/hr.v of carbonization water which also is at a temperature of 80 C. and in its turn Icontains 1% The mixture of the two streams of water at a rate of 29 m.3/hr. containing about 1.6% phenols passes into the separator in which 70 kg./hr. of neutral oil separate out. The aqueous phase is preheated to 92 C.

by heatexchange and enters, at this temperature, into the stripping column. Here steam ilows in countercurrent to the mixture and between 600-1000 kg. of disseparator 39 in which small quantities of oil, 'which may separate out of solution due to the reduction of tempera-y Y aqueous extract, which additionally contains quantities of the neutral oil, pass by means of the vline 44 and pre'-y heater 51 into the distillation column 52.I Steam is passed through the column 52 from the inlet53 at a temperature, for example, suicientto maintain the'sump of the column at about 100 C. and in the head of th column at about 90 C.

In the column the neutral oils are distilled o if from vthe aqueous phenolic solution4 and pass in the f orrn of an azeotropic mixture with water vapor through the line 54 into the cooler S5. Ater cooling in the cooler 55,

the mixture flows into a separator 56 in which the condensate separates into water and neutral oils. The latter leaves the installation through the outlet 57 while the water is returned through the line 58 into the column 52.

In the column 52 carbon dioxide and hydrogen sulide, which are generally additionally present in the oil fraction and thus the extract being treated, are carried over with the vapor and separated in the separator leaving the same through the line 59, by means of which the same passes to the lower portion of the washing tower 62. At the same time, the aqueous phenol solution, which has been freed from the neutral oils, pass from the sump of column 52 through the cooler 60 and line 61 to the top of the washing tower 62, where the same flows down in counter-current to the carbon dioxide and hydrogen sulfide-containing gases. The interaction between the gases and the aqueous phenol solution has the advantage that the phenol solution, the pH of which is increased during the distillation, is again reduced to a value of about 8 to 8.5, which renders the same suitable for a subsequent treatment with a solvent. The solution then passes out of the tower 62 through the line 63 into the extraction installation 4S of conventional construction. In this extraction apparatus the phenols are separated from the water with the use of an organic solvent, as, for example, butylacetate. The phenols obtained are 4tillate p er hour pass over at a head temperature of 93 98 C. The oil condensate is obtained in a quantity of 20'-80kg./hr. It consists of neutral oil of a boiling range vof 150-210 C. and contains 160-200 grams per kg. of phenols and 10-l5 grams per kg. of ammonia.

- The quantity of phenol also passing over upon the azeotropic distillation is a maximum of 2% of the total quantity. The oil condensate of the azeotropic distillation is returned to the pressure extraction. The sump temperature in the stripping column varies between 98 l00 C.

y The sump product is cooled down by heat exchange to the extraction temperature of about 30-40 C. It still containsonly 0.1 gram neutral oil per liter. In an extraction plant it is freed of phenol in the customary manner with butylacetate and part of the dephenolated carbonization water passes as solvent back into the hot water extraction.

The composition of the crude phenol obtained by pressure extraction from the light oil fractions of l50210 C. is as follows:

The yield of phenols from the dilute aqueous extract is more than 99.5%. The crude phenol mixture which consists of the phenols present in the carbonization water and in the oil has a neutral oil content of between 0.6- 1%. By refining and distillation, the crude phenol mixture can be worked up into high grade finished products.

The invention not only has the advantage that the neutral oil fraction, as, for example, boiling between 230 C., is extensively freed of the acid components, and that `a phenol-poor neutral oil is obtained, but in addition it has the important advantage that phenols of high quality are obtained from this extraction. The invention makes it possible at the same time to increase the total yield of phenols obtained in the process since the mixed phenol-containing water as, for example, the carbonization water, i.e. thin water mixed with the aqueous extract, can be treated as, for example, by extraction so aesaaet that only a very small residual phenol content remains.

While the invention has been described in detail with reference to the specific embodiment shown, various changes and modications will become apparent to the skilled artist and which fall within the spirit of the invention and the scope of the appended claims.

We claim:

l. In the method for the separation of phenols and neutral oils from their mixture by contacting with hot water at a temperature of at least 100 C. and a pressure in excess of the vapor pressure of the mixture formed, for the extraction of phenols with the recovery of an aqueous extract containing phenols and dissolved neutral oils, the improvement for separating the neutral oils from the phenols in the aqueous extract, which comprises diluting said aqueous extract with an additional amount of water and cooling the extract to below 100 C. and thereafter distilling the neutral oils as an azeotropic mixture with water from the resulting diluted aqueous extract, leaving an aqueous solution of phenols substantially free from said neutral oils, said dilution being effected with an additional amount of water sucient to maintain the phenols dissolved at the lowest temperature below 100 C. encountered prior to said distilling off of the neutral oils.

2. Improvement according to claim 1 in which said additional amount of water for said dilution is a phenolcontaining water.

3. Improvement according to claim 2 in which said phenol-containing Water is a phenol waste water not containing substantially an excess of about 1% of phenols.

4. Improvement according to claim 1 which includes cooling said aqueous extract to a temperature between about 60-90 C. prior to said distillation, and in which said dilution is eiected with an additional amount of Water sufficient to maintain the phenols dissolved at said temperature.

5. Improvement according to claim 4 in which said cooling is at least partially effected by said dilution.

6. Improvement according to claim 5 which includes removing separated neutral oils by layer formation after said cooling and prior to said distilling.

7. Improvement according to claim 6 which includes extracting phenols from said aqueous solution of phenols after said distillation with the use of an organic solvent, and recovering the phenols substantially free from neutral oils.

8. Improvement according to claim 7 in which the carbon dioxide and hydrogen sulde distilled over with said azeotropic mixture are separately recovered and contacted with the cooled phenol-containing water from which they were distilled.

9. Improvement according to claim 1 which includes extracting phenols from said aqueous solution of phenols after said distilling with an organic solvent and recovering the phenols substantially free from neutral oils.

10. Improvement according to claim 9 in which said extraction is effected with butylacetate,

l1. Improvement according to claim 1 in which said distillation is eiected at about normal pressure.

12. Improvement according to claim 11 in which said distillation is eiected by passing said extract downwardly in nally divided form in contact with upwardly moving steam.

13. Improvement according to claim 1 in which said azeotropic distillation is a steam distillation.

14. Improvement according to claim 1 in which said cooling is at least partially effected by said dilution to a temperature between about -90 C.

l5, Improvement according to claim 1 in which said dilution is effected with about 2-6 volumes of water per volume of extract.

16. ln the method for the separation of phenols and neutral oils from their mixture by contacting with hot water at a temperature of at least C. and a pressure in excess of the vapor pressure of the mixture formed, for the extraction of phenols with the recovery of an aqueous extract containing phenols and dissolved neutral oils, the improvement for separating the neutral oils from the phenols in the aqueous extract, which comprises distilling the neutral oils as an azeotropic mixture with water from the aqueous extract in the presence of suicient diluting water to maintain the phenols dissolved, 1

leaving an aqueous solution of phenols substantially free from said neutral oils.

References Cited in the file of this patent UNITED STATES PATENTS 2,086,856 Deiters et al. July 13, 1937 2,199,786 Dierichs et al. May 7, 1940 2,209,150 Byrns July 23, 1940 FOREIGN PATENTS 359,013 Great Britain Oct. 12, 1931 517,618 Great Britain Feb. 5, 1940 

1. IN THE METHOD FOR THE SEPARATION OF PHENOLS AND NEUTRAL OILS FROM THEIR MIXTURE BY CONTACTING WITH HOT WATER AT A TEMPERATURE OF AT LEAST 100* C. AND A PRESSURE IN EXCESS OF THE VAPOR PRESSURE OF THE MIXTURE FORMED, FOR THE EXTRACTION OF PHENOLS WITH THE RECOVERY OF AN AQUEOUS EXTRACT CONTAINING PHENOLS AND DISSOLVED NEUTRAL OILS, THE IMPROVEMENT FOR SEPARATING THE NEUTRAL OILS FROM THE PHENOLS IN THE AQUEOUS EXTRACT, WHICH COMPRISES DILUTING SAID AQUEOUS EXTRACT WITH AN ADDITIONAL AMOUNT OF WATER AND COOLING THE EXTRACT TO BELOW 100* C. AND THEREAFTER DISTILLING THE NEUTRAL OILS AS AN AZEOTROPIC MIXTURE WITH WATER FROM THE RESULTING DILUTED AQUEOUS EXTRACT, LEAVING AN AQUEOUS SOLUTION OF PHENOLS SUBSTANTIALLY FREE FROM SAID NEUTRAL OILS, SAID DILUTION BEING EFFECTED WITH AN ADDITIONAL AMOUNT OF WATER SUFFICIENT TO MAINTAIN THE PHENOLS DISSOLVED AT THE LOWEST TEMPERATURE BELOW 100* C. ENCOUNTERED PRIOR TO SAID DISTILLING OFF OF THE NEUTRAL OILS. 